getpagesize() - Unix, Linux System Call

NAME

SYNOPSIS

DESCRIPTION

The function
getpagesize() returns the number of bytes in a page, where a "page" is the thing
used where it says in the description of
mmap(2)
that files are mapped in page-sized units.

The size of the kind of pages that
mmap() uses, is found using

#include <unistd.h>
long sz = sysconf(_SC_PAGESIZE);

(where some systems also allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE),
or

#include <unistd.h>
int sz = getpagesize();

HISTORY

This call first appeared in 4.2BSD.

CONFORMING TO

SVr4, 4.4BSD, SUSv2.
In SUSv2 the
getpagesize() call is labeled LEGACY, and in POSIX.1-2001
it has been dropped.
HP-UX does not have this call.

NOTES

Whether
getpagesize() is present as a Linux system call depends on the architecture.
If it is, it returns the kernel symbol PAGE_SIZE,
which is architecture and machine model dependent.
Generally, one uses binaries that are architecture but not
machine model dependent, in order to have a single binary
distribution per architecture. This means that a user program
should not find PAGE_SIZE at compile time from a header file,
but use an actual system call, at least for those architectures
(like sun4) where this dependency exists.
Here libc4, libc5, glibc 2.0 fail because their
getpagesize() returns a statically derived value, and does not use a system call.
Things are OK in glibc 2.1.